Control device



1952 c. G. KRONMILLER 2,613,105

CONTROL DEVICE Filed nemf zs, 1948 '2 SHEETSSHEET 1 INVENTOR. CARL G.KRONMILLER 'ATTORNE Y Oct. 7, 195 2 C. G. KRONMILLER 2,613,105

CONTROL DEVICE Filed Dec. 23, 1948 2 SHEETSSHEET 2 INVENTOR. CARL G.KRONMILLER BY 63 48 fiwflM Arron/v5) Patented Oct. 7, 1952 UNITED STATESrA'rENT OFFICE GQNTROL DEVICE Carl G. .Kronmiller, Edina, Minn, assignorto Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application December 23, 1948, Serial No. 67,608

3 Cl ims- 1 This invention is directed to condition responsive controldevices and more particularly to adjusting means for such devices.

It is an object of the invention to provide an adjusting mechanism for acondition responsive device, such as a room thermostat, in which thecontrol temperature is adjusted by manually po sitioning a slidablemember that extends through an opening in the instrument cover.

Another object is to provide a room thermostat or similar control devicein which the base of the instrument carries a bracket on which ismounted a scale plate, a thermometer cooperating with the scale, andanadjusting member which is manually movable in the bracket and isprovided with a pointer which cooperates with the same scale. The scale,pointer and thermometer may be visible through a suitable window in theinstrument cover and the adjusting member may be constructed with aportion that extends through an opening in the cover to facilitatemanual selection of the control temperature.

Another object of the invention is to provide a room mounted controldevice having a window in the cover through which the conditionindicatingscale may beviewed, the cover being otherwise opaque toconceal the operating mechanism. This structure may comprise a coverfabricated of transparent material which is coated with opaque materialexcept in the area that overlies the scale.

Other objects will be evident irom the written description and appendedclaims, and from the drawing, in which v Figure l is a front elevationof aroomthermostat incorporating the invention with the cover in place.

Figure 2 is a plan view of the base and adjusting mechanism of thethermostat, with other parts omitted.

Figure 3 is an elevation, similar to Figure l, but with the coverremoved and certain parts broken away. I I

Figure i is an elevation as seen from the left of Figure with the coverin place but shown in section.

Figure 5 is a plan view of the device with the cover in place, and

Figure 6 is an enlarged fragmentary section of a portion of the coverincluding the window that overlies the scale plate.

In the illustrative embodiment of the invention the control point of abimetal actuated thermostat is adjusted by a manually slidable memberextending through a slot in the cover of the device. The slot preferablyis one of a plurality of openings in the cover provided to permit roomair to circulate over the tempera ture responsive element. The slidablemember is guided by a bracket which also carries a scale plate and athermometer adjacent the front of the cover. A window is provided in thecover through which the thermometer and scale plate together with apointer positioned by the movable member may be viewed. This arrangementpermits a single scale to be used to indicate both selected and actualtemperatures without the necessity for accurately correlating theposition of parts mounted on the base with re spent to the cover aswould be the case if either the scale plate or the thermometer or bothwere carried on the cover 'Also, all the operative parts of the devicemay be assembled on the base and calibrated before the cover isattached.

My patent Des. 157,687 is directed to the outward appearance of thisthermostat.

- The device illustrated in the several figures of the drawing has abase I!) of electrically insulating material adapted to be secured tothe wall of a room. As seen in Figure 3, a stationary contact Ii and apermanent. magnet l2 are secured to the base by a conducting bracket i3,contact H being screw-threaded in the bracket l3 to provide anadjustment of operating differential. The bracket I3 is provided with aterminal screw M. A movable contact 55, which cooperates with thestationary contact H is secured to the right hand end of a spring stripIt, the left hand end of which is secured to a bracket l! which is fixedto the base It. A switch arm I8 is secured to the strip 16 adjacent itsattachment to the bracket 51, the right hand end of this arm beingprovidedwith an opening through which the movable contact i5 extends.When the contacts ii and [5 are in engagement, the contact carrying endof the spring strip I 6 is pressed back from the arm It tolassurepredetermined minimum pressure between the contacts. This switchingmechanism is disclosed in my copending application Serial No. 681,461filed July 5, 1946, now Patent Number 2,493,294.

A U-shaped bimetal element 89 is pivotally secured to the bracket i'i bya spring strip 213. The lower arm of bimetal element engages anextension 22 of the switch arm 18 in a manner adapted to move thecontact it out of engagement with contact ii. The switch am: It is ofmagnetic material and is biased by the magnet l2 toward contact" closingposition. The movable Contact I5 is electrically connected by the strip[6, the bracket 11, an extension a of the spring strip 20 and aconductor 23 to a terminal screw 24 on the base ID.

The upper leg of the U-shaped bimetal element [9 is provided with anadjustable screw abutment 26 that engages a cam 21 which is horizontallyslidable in a bracket 30 to adjustably position the extremity of theupper leg of the bimetal element l9. The strip 20 which supports thebimetal element and the portion of strip [5 which supports switch arm I8are so formed that the attraction of the magnet l2 for switch arm l8will maintain the abutment 26 in engagement with cam 2'! at alloperative conditions of the switch. Hence, the adjusted position of thecam 21 determines the temperature at which the contact IE will beactuated by the bimetal element.

The cam 21 is formed integrally with a member 3| which is carried by apair of parallel strips 30a and 30b that form a part of bracket 30. Thestrip is integral with the bracket 30 and strip 3% is secured thereto bya screw at either end. Preferably the openings in the bracket 30 throughwhich the screws pass are somewhat enlarged to permit a small amount ofadjustment of the strip 30b with respect to the strip 30a. Cam 2!extends downwardly between the strips and is provided with a pin 32 thatserves as an abutment for a curved spring strip 33 which exerts anupward force on a friction plate 34 that engages the underside of theparallel strips 30a and 301). A manually positionable knob 35 isintegral with the member 3| and cam 21 and serves to position cam 27 tothe right or left as seen in Figures 2 and 3. The bracket 38 alsocarries a scale plate 3! having indicia of temperature thereon. Apointer 38, which is movable with the cam 21 cooperates with the indiciaon the scale plate 3! to indicate the control temperature of thethermostat. lThe thermostat is calibrated by adjusting screw abutment 26so that the bimetal l9 will actuate the switch at the temperatureindicated by the pointer 38 on the scale plate 31. A thermometer tube 40is also carried by the bracket 30 adjacent the lower edge of the scaleplate 31 and cooperates with the indicia thereon to indicate actual roomtemperature. Scale plate 31 is preferably made of translucent materialto facilitate illumination of the indicia thereon as will appear below.

An anticipating heater in the form of graphite cylinder 43 is secured tothe bracket l1 and to the strip 20, the arrangement being such that whenthe heater is energized heat will be conducted through the strip 20 tothe bimetal element I9. The upper end of the heater 43 is connected by aconductor 44 to a terminal strip 45 on the base [0. A terminal screw 46is provided to facilitate external connection. A resilient extension 45aof the terminal strip 45 is adapted to be moved by a button 48 intoengagement with the center terminal of a light bulb 49, the conductingbase of which is supported by spring fingers 58a of a terminal strip 50secured to the base 10. The terminal strip 50 is provided with aterminal screw 5!.

A typical control circuit has been illustrated in connection with Figure3 to facilitate understanding of the various parts of the device. Acontrol valve 55, which is adapted to control the supply of heatingmedium to the room in which the thermostat is located, is connected by awire 56 to the thermostat terminal 24 and by a wire 51 to the secondaryof a transformer 58. The

opposite terminal of the transformer secondary is connected by a wire 59to the thermostat terminal l4. It will be seen that when the thermostatcontacts ll-I5 are in engagement a circuit will be completed to energizethe valve 55 and supply heat to the room. Likewise, when the contacts|--I5 are in engagement the heater 43 will be energized through a wire51a connected to the terminal screw 46 and thence through the terminalstrip 45, conductor 44, heater 43, bracket ll, spring strip [6, contacts|5| l, bracket [3, terminal screw l4 and wire 53 which leads back to thetransformer 58. When the button 48 is pressed inwardly to cause theresilient portion 45a of terminal strip 45 to engage the center terminalof the lamp, the transformer will energize thelamp 49 through wires 51and 51a, terminal strip 45, resilient extension 45a, lamp 49, terminalstrip 50, terminal screw 5|, a conductor 59a, and the wire 59 to theopposite transformer secondary terminal. The light supplied by the lamp49 serves to illuminate the scale plate 5'! so that the indicia thereonwill be visible to permit both the actual room temperature andthermostat setting to be ascertained. It has been found that the bestlocation for a room thermostat is often in a position that affords poorvisibility even in the daytime. Likewise, the self contained lightsource is desirable to facilitate setting a room thermostat at nightwithout turning on the light that supplies general room illumination.

A cover 6|, that encloses the various operative parts of the device aswell as the scale plate 31 and the thermometer tube 40, is secured tothe base [0 by a pin 62 extending from the top of the base and by ascrew 63 which is screw-threaded in the lower edge of the base In andpasses through a slot in cover 6!. The cover 6| is provided witha'plurality of openings 35 in the top theerof as best seen in Figure 5and a plurality of openings 66 in the bottom, which openings areprovided to permit circulation of room air through the enclosure formedby cover Bi and the base It] and over the bimetal element [9 and thethermometer tube 40 so that they will accurately follow changes intemperature of the room air. The knob 35 which serves to manuallyposition the cam 21 extends upwardly through an elongated opening 65a inthe top of cover 61. This opening 65a is of suflicient length so thatcam 21 may be moved through the full range of adjustment permitted bythe length of the opening between the strips 30a and 30b of the bracket30.

v The cover 6| is preferably molded of a clear synthetic resin such asLucite. In order to conceal the mechanism of the thermostat the interiorof the cover is coated with a layer of opaque material such as paint 66over the entire interior surface thereof with the exception of an areaoverlying the indicia on the scale plate 37. Thus, the opening in theopaque layer provides a window 68 through which the indicia on the scaleplate 37 together with the pointer 38 and the thermometer tube 40 may beviewed. In Figure 6 an enlarged section of the portion of the coveroverlying the scale plate is shown, the thickness of the opaque layerbeing somewhat exaggerated for the purpose of illustration. Thisconstruction provides a simple way of providing a generally opaque covertogether with a window through which the indicia may be viewed. It ismerely necessary to mask the window portion of the cover prior tospraying the interior of the cover with asuitable paint. The provisionof a transparentwindow over the scale and pointer prevents aimlesstampering with these portions of the device. portion of the coverintegral with the remaining portions thereof, the strength of the coveris materially increased. The cover is sufficiently thin so that itpresents an appearance of being made of a material of the color of thepaint applied to its inner surface.

While the invention has been described in connection with a bimetalactuated electric switch, it will be apparent that the adjusting meansprovided would be equally applicable to the other types of thermostatsor to other condition responsive devices, as for example, a humiditycontrol. It is not necessary that the condition responsive elementitself be adjusted by the cam. An equivalent adjustment could beobtained by changing the position of a normally stationary contact, inwhich case the thermostatic element would remain in fixed relation tothe instrument base.

While the cam has been described as sliding in a bracket attached to thebase, and the scale plate has been described as supported by a bracket,it will be apparent that certain phases of the invention would beinvolved if the base itself was formed to carry these members. Variousother modifications will be apparent to those skilled in the art and thescope of the invention therefore is to be limited only by the scope ofthe appended claims.

I claim as my invention:

1. In a condition control device, a base adapted to be mounted on thewall of a room, a condition responsive means positioned on said base,said condition responsive means having an adjustable portion theposition of which determines the control condition value, a bracket onsaid base having parallel members forming a longitudinal track, a slidercarried by said members and movable along the track provided thereby,said track having parallel inner and outer faces, said slider having amanually engageable portion and hav- Likewise, by molding the window inga cam operatively engaging the adjustable portion of theconditionresponsive means, said slider having a rigid track engagingportion movable along the outer faces of the track, said slider alsoincluding resilient biasing means engaging the inner faces of the trackfor holding said rigid track engaging portion firmly against the outerfaces of the track forming members, a scale plate bearing indicia of thecondition carried by said bracket and arranged parallel to said track,and a pointer carried by said slider and movable along said scale plate.

2. A control device as defined in claim 1 where in one of said parallelmembers is readily removable and wherein the rigid track engagingportion of the slider and the cam are unitary.

3. A control device as defined in claim 1 in which an enclosing coverhaving an outline similar to the base of the control device is arrangedover the condition responsive means and is attached to said base, saidcover having upper and lower slots, at least one of the upper slotsbeing parallel to said track and arranged so that the manuallyengageable portion of the slider extends through said one slot, saidcover also having a Window coextensive with at least a portion of theindicia of said scale plate through which the indicia and the pointermay be observed.

CARL G. KR'ONMILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

